The primary objective of the research proposed herein is the identification of the determinants of virulence (virulence factor(s)) of Gram negative corroding anaerobic/microaerophilic bacteria that have been implicated in periodontal disease. It is proposed to initially investigate the occurrence of virulence factors in strains of two Gram negative, corroding organisms, Eikenella corrodens and Bacteroides corrodens, both being isolated in significantly elevated numbers in patients diagnosed to have aggressive periodontal disease. Recent studies have demonstrated that certain microorganisms produce mediators which behave, in many but not all respects, like mediators (lymphokines) produced by sensitized lymphocytes. Such mediators have been implicated in a number of pathological reactions. Thus, the initial studies of this project will be directed towards the determination of whether selected strains of E. corrodens and B. corrodens produce and/or release lymphokine-line mediators. Preliminary data indicates that the spent culture fluids of these organisms possess both macrophage migration inhibition and chemotactic mediator activities. Studies will be undertaken to determine further if these microorganisms produce and release lymphokine-like mediators into their environment or whether such factors are components of the outer cell envelope. Filtrates of spent culture media and components of the cell envelope will be assessed using in vitro assays for the following mediator activities: chemotactic activity, migration inhibition for macrophages and neutrophiles, mitogenic activity and cytotoxic activity. It is proposed to isolate such lymphokine-like mediators using chromatographic techniques. Furthermore, to correlate production/release of such mediators it is proposed to demonstrate their in vivo production/release and to demonstrate that administration of purified preparations of such mediators when administered via injection into the gingival tissue of rats produce histological changes consistent with those noted in the infection with whole microorganisms. In addition, it is proposed to select for strains initially on the basis of colonial morphology which fail to produce lymphokine-like mediators and to determine if these strains can infect and produce a disease profile similar to that induced by known virulent progenitor strains.